Transformer ballast assembly for energizing gas discharge devices



May 5, 1964 N. oULETTA 3,132,285

TRANSFORMER BALLAST ASSEMBLY FOR ENERGIZING GAS DISCHARGE DEVICES original Filed March 22, 1957 Patented May 5, 1964 3,132,285 TRANSFORMER BALLAST ASSEMBLY FOR ENER- GIZING GAS DISCHARGE DEVICES Nicholas Ouletta, Melrose Park, Ill., assignor to Jefferson Electric Company, Bellwood, Ill., a corporation` of Delaware Original application Mar. 22, 1957, Ser. No. 647,771, now Patent No. 3,107,317, dated Uct. 15, 1963. Divided and this application Dec. 30, 1960, Ser. No. 79,689 9 Claims. (Cl. 315-254) This invention relates to ballasts for gaseous discharge lamps, such as iluorescent lamps, and to a system embodying the same'.

It pertains more specically to such ballasts as are of the high reactance step-up transformer type which supply the arc discharge device in series with a condenser. In such a circuit, the capacitive reactance predominates so that a ballast of this nature will have a power factor of the leading type probably lower than 90%. In order to correct the power factor of such a device, it is necessary to introduce lagging current or v.a. approximately equal to the leading current or v.a. This can be accomplished by introducing an air gap in the magnetic circuit of the transformer.

The present application is a division of my copending application, Serial No. 647,771 filed March 22, 1957, now Patent No. 3,107,317, granted October 15, 1963, which, in turn, is a continuationdn-part of my then copending application, Serial No. 309,599, filed September 15, 1952, now abandoned, in which it is pointed out that improved results are obtained if the gap is a bridged gap which provides a magnetically saturated core portion. More specically, said then copending application discloses the use of a shell type core in which the bridged gap is in the form ofl a closed slot located in the winding leg, and it further points out that by proper location of the slot, greatly improved results can be obtained, particularly with respect to wave shape of ballast which employs a starting winding, as shown in FIG. 4 hereof.

An advantage resulting from the practice of my invention lies in the fact that due to the location of the gap, it can be constructed in the form of a slot in the core, rather than in the form of a bridge at the joint between two core portions or stack sections, thus providing a more secure joint.

An object of my invention is to provide an improved gapped core structure in which all abutting stack surfaces are solid, as contrasted with a core structure which is gapped at a joint.

Still another object is to provide an improved ballast which eliminates or reduces hum, and which may be assembled with greater ease and constructed with less cost than comparable prior art ballasts.

The invention is herein shown in FIGS. 1 and 2 with respect to a capacitive ballast of the rapid start type, which is to say a capacitive ballast which does not employ the separate starting winding of FIGS. 3 and 4.

With reference now to the drawings in which like reference numerals designate like parts:

FIG. 1 is a plan view of the core structure showing the location of the primary and secondary windings in dotted lines;

FIG. 2 is a wiring diagram of the ballast;

FIG. 3 is an elevation of the core structure of another type of ballast embodying my invention; and

FIG. 4 is a wiring diagram showing a type of circuit for the ballast of FIG. 3.

With reference now to FIG. 1 which shows the core structure of the high reactance transformer, reference numeral designates the winding leg, and the reference numerals 11 and 12 designate the yoke portions. These elements are built up of laminations of the T and L types.

rihe resulting shell type core structure provides windows 13 in which are disposed the primary winding 14 and the secondary winding 15, both shown in dotted lines. In the particular design shown, no separate shunt yportion is provided, since a leakage path 22 is provided by the mere juxtaposition of the two windings, although a magnetic shunt type of path may be provided if desired, as shown in FIG. 3. Actually, the windings are spaced from each other by about a quarter inch, since in winding the coils the paper separator extends beyond each coil layer by approximately one-eighth inch.

Those portions of the winding leg which are surrounded by the primary and secondary windings can be referred to as the primary portion 16, and the secondary portion 17, respectively.

A slot 18 is located in the secondary portion`17 at a position such that its effective center line is substantially 48 percent of the distance from the center line of the leakage path 22 to the remote end of the secondary core portion 17.

As shown in FIG. 2, the primary and secondary windings 14 and 15 are connected in auto-transformer relationship, and the circuit includes a condenser 26, and two 1 uorescent lamps 27 connected in series circuit with each other and with condenser 26 and the windings 14 and 15.

The saturable core portions 23 adjacent the ends of the slot 1S contribute to the mechanical strength of the particular stack in which the slot is formed, thus, reducing the tendency to stack hum. It can be pointed out at this point, that there is virtually no casing hum at casing 28, since any stray tlux at the periphery of the core is practically eliminated. Furthermore, by providing solid abutting surfaces at the joints, stack hum is further reduced beyond that which is present where a bridged gap is located at the joint.

The foregoing paragraph also applies to the core structure of FIG. 3 which has magnetic shunts 113 and 114 and to the circuit of FIG. 4 which includes a starting winding 134.

The subject matter of the aforesaid then copending application, Serial No. 309,599 is incorporated herein by reference, insofar as consistent with the present disclosure.

Although only a preferred embodiment of my invention is shown and described herein, it will be understood that modiiications and changes can be made in the embodiment shown without departing from the spirit of my invention as pointed out in the appended claims.

With reference now to FIG. 3, the reference numeral designates generally a core which comprises a winding leg 111 and yoke portions 112. The yoke portions are provided with shunt portions 113 and 114 which are preferably formed integral with the yoke portions, thus dividing the interior of the core into three pairs of windows 115, 116 and 117 which are adapted to receive the ballast windings. It will be observed that the shunt portions 113 and 114 are separated from the winding leg 111 by gaps 118 and 119, respectively.

It will be understood that the core 110 is made up ofy stacks of substantially identical laminations as is the standard practice. The ends of the winding leg stack and the yoke portion stacks are mitered as indicated by reference numeral 120 and the laminations of each stack n may be secured to each other, and each stack may be secured to its adjacent stack or stacks by means of welds 121, this type of construction being pointed out in copending Anderson application, Serial No. 254,027, tiled October 31, 1951, owned by the assignee herein, and now abandoned. Thus, the several stacks or core portions are rigidly abutted to each other in such a manner that amazes the gaps 118 and 119 may be held to predetermined dimensions.

A bridged gap 122 is formed in one of the secondary portions of the winding leg 111. This bridged gap is in the form of a closed slot 123, adjacent the ends of which are saturable portions 124. According to my invention, the bridged gap is located close to the gap 119 or to the flux path traversing the same, but it is not located directly beneath the gap 119.

In other words, assuming that the core 111i is divided into three portions, a starting portion 137, a primary portion 133 and a secondary portion 139, the slot 123 is offset from the primary portion so that it is located in the secondary portion at a point offset from the flux leakage path by a distance not exceeding 25% of the length of the window 117.

The core 11@ as pointed out previously, is adapted to be used in a ballast having a leading load circuit. The wiring diagram for one type of such a ballast is shown in FIG. 4. Here, a primary winding 125 is connected between the supply lines 126 and 127. A secondary winding 128 is connected in autotransformer relationship to the primary Winding 125 by means of suitable conductors 129 and 131i. The load circuit of the ballast includes one or more gaseous discharge devices, such as duorescent lamps 131 and 132, and a condenser 133. In the particular circuit shown, two lamps are provided, one being interposed in the conductor 129, and the other being interposed in the conductor 130, so that the two lamps are separated by the secondary winding 128. The condenser 133 is also interposed in the conductor 13d so that it is connected in series with the lamp 132 as well as with the secondary 128 and the lamp 131. Starting is facilitated by a starting winding 134 which is connected between the point 135 on supply line 126 and a point 136 in conductor 131i. By virtue of this starting coil, a high starting voltage is first applied to lamp 132 and after this has been ignited, the lamp 131 will then be ignited. This particular circuit arrangement is shown in Feinberg Patent No. 2,558,293, dated inne 26, 195i.

ln applying the above circuit to the present invention, the starting winding 134 is disposed in window 115, the primary winding 125 is disposed in window 115, and the secondary winding, or operating winding 12S is disposed in window 117. The shunts 113 provide a low reluctance path between the starting winding 13d and the primary winding 12S. The shunts 11d provide a low reluctance path between the primary winding 125 and the secondary or operating winding 12,8. This latter low reluctance path is the usual flux leakage path which is characteristically provided in ballasts and high reactance transformers between the primary and secondary wind ings, and which imparts a high inductive reactance to the secondary circuit.

In some situations, it is possible to obtain the desired leakage without providing the shunt portions 114.

In the particular type of ballast to which this invention relates, this inductive reactance of the secondary circuit is more than offset by capacitive reactance of the condenser 133, so that the net load is capacitive, thus providing a capacitive ballasting action.

I claim:

l. In apparatus for igniting and operating gaseous discharge devices which includes a condenser,

a metal canister having at least a transformer therein with leads extending from said canister for connection to said gaseous discharge devices and a source of alternating current voltage,

said transformer having an elongate shell-type core with a rectangular frame portion and a central winding leg,

windows along the length of the core and said transformer having at least, a primary winding and a secondary winding, disposed in said windows and each winding encircling and enclosing a different portion of said winding leg, and

said' secondary winding being connected with said condenser and the circuit constants being of value such that a leading current will flow through said secondary during operation;

the improvement which comprises the ends of the central winding leg abutting with the ends of the frame portion in magnetic connection therewith, and

a transverse non-magnetic gap in that portion of said central winding leg encircled by said secondary winding.

Y 2. In an apparatus for igniting and thereafter providing the operating voltages for gaseous discharge device means and which includes an elongate iron core having a central winding leg,

an outer rectangular framing part,

windings including at least a primary winding and a secondary kwinding arranged encircling the winding leg along the length thereof,

the ends of the winding leg engaged with the ends of the outer framing part,

a condenser,

a canister housing the core, and windings,

connections between gaseous discharge device means external of the canister, said windings, condenser and a source of voltage forming a circuit in which a leading current flows through said secondary winding during operation of said gaseous discharge device means, and

a non-magnetic gap in said core in the vicinity of said secondary winding to limit the ux thereat;

means for limiting the fringing of llux to said canister by reason of said non-magnetic gap whcih comprises said gap being formed of a transverse slot in said winding leg between the ends of and confined by said secondary winding.

'5. A structure as claimed in claim 2 in which the slot is closed at both ends thereof.

4. A structure as claimed in claim 2 in which the secondary Winding is adjacent one end of the winding leg, and there is a shunt including a second non-magnetic gap separating the secondary winding from its next adjacent winding andthe slot is located in said winding leg between the said one end and the said shunt.

5. Apparatus for igniting and operating a pair of gaseous discharge devices which comprises,

a condenser,

a metal canister having at least a transformer therein with leads extending from said canister for connection to gaseous discharge devices and a source of alternating current voltage,

said transformer comprising an elongate shell-type core having a rectangular frame portion and a central winding leg,

three windows formed along the length of the core and two gapped shunts separating the windows,

the ends of the Winding leg abutting in magnetic connection with the ends of the frame portion,

a primary winding in the center window and secondary windings in the windows on opposite sides of the primary winding, and

a transverse non-magnetic gap in the central winding leg spaced from an abutting magnetic connection and completely covered by a secondary winding.

6. Apparatus as claimed in claim 5 in which said last secondary Winding is connected in series with said condenser and, said apparatus includes a pair of series con- Ei nected gaseous discharge devices outside of said canister in serieskwith said last secondary winding and together therewith connected in auto-transformer relation across the primary winding.

7. Apparatus for igniting and operating gaseous dis charge devices which comprises,

a metal canister of elongate configuration, a transformer having an elongate shell-type laminated core, including a substantially rectangular framing part and a central winding leg disposed in the framing part and having its ends abutting the opposite ends thereof, a primary winding and at least two secondary windings, a series-sequence starting and substantially series operating circuit formed with said windings and including at least two gaseous discharge devices energized by said windings and t a condenser, winding carrying windows formed in said framing part along the length thereof alongside the winding leg and shunts separating the windows, the primary winding being disposed inthe center window and having the secondary windings in windows on opposite sides thereof, one secondary winding providing substantially greater leakage reactance thanfthe other and having a greater number of turns than the other to aid in ignition but resist current ow therethrough during operation, the second secondary winding serving to carry substantially all of the operating current and being connected in series with said condenser and discharge devices during operation, and a bridged non-magnetic gap in the winding leg transverse thereof,

spaced from an abutted end, said gap being completely covered by said second secondary winding, said transformer being enclosed within said canister. 8. A transformer provided ywith a magnetic core having an outer rectangular frame portion,

a central insert winding leg magnetically connected and physically abutted against the ends of the frame .portion on the interior thereof,

three windows each having two parts on opposite sides ofthe winding leg, y

two shunts separating the windows along the length of said winding leg and having facing extensions forming nonnnagnetic gaps with the leg,

three generally cylindrical coils mounted in the windows and comprising a primary winding and two secondary windings with the primary winding in the center with their axes coincident,

a metal canister surrounding the transformer, and

a slot in the winding leg extending therethrough arranged transverse of the length thereof and located between the ends of a secondary winding considered along its axis and completely enclosed thereby.

9. Apparatus as claimed in claim 8 in which there are provided a pair of gaseous discharge devices and a source of alternating current voltage,

all external of the canister, and

a condenser, and

the primary winding is connected across the source,

the secondary windings are connected end to end after the primary winding,

a discharge device is connected in series with the condenser and together therewith across the primary winding and the next following secondary winding,

the second discharge device is connected across both secondary windings together, and

the second following secondary winding is the winding above referred to which encloses said slot.

References Cited in the file of this patent UNITED STATES PATENTS 2,355,360 Boucher Aug. 8, 1944 2,774,011 Feinberg Dec. l1, 1956 2,920,237 Berger Jan. 5, k1960 

1. IN APPARATUS FOR IGNITING AND OPERATING GASEOUS DISCHARGE DEVICES WHICH INCLUDES A CONDENSER, A METAL CANISTER HAVING AT LEAST A TRANSFORMER THEREIN WITH LEADS EXTENDING FROM SAID CANISTER FOR CONNECTION TO SAID GASEOUS DISCHARGE DEVICES AND A SOURCE OF ALTERNATING CURRENT VOLTAGE, SAID TRANSFORMER HAVING AN ELONGATE SHELL-TYPE CORE WITH A RECTANGULAR FRAME PORTION AND A CENTRAL WINDING LEG, WINDOWS ALONG THE LENGTH OF THE CORE AND SAID TRANSFORMER HAVING AT LEAST, A PRIMARY WINDING AND A SECONDARY WINDING, DISPOSED IN SAID WINDOWS AND EACH WINDING ENCIRCLING AND ENCLOSING A DIFFERENT PORTION OF SAID WINDING LEG, AND SAID SECONDARY WINDING BEING CONNECTED WITH SAID CONDENSER AND THE CIRCUIT CONSTANTS BEING OF VALUE SUCH THAT A LEADING CURRENT WILL FLOW THROUGH SAID SECONDARY DURING OPERATION; THE IMPROVEMENT WHICH COMPRISES THE ENDS OF THE CENTRAL WINDING LEG ABUTTING WITH THE ENDS OF THE FRAME PORTION IN MAGNETIC CONNECTION THEREWITH, AND A TRANSVERSE NON-MAGNETIC GAP IN THAT PORTION OF SAID CENTRAL WINDING LEG ENCIRCLED BY SAID SECONDARY WINDING. 